PubMed · 4479080
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J M Thijssen, A Pinckers. 1974. Contralateral effects in the electro-oculogram.. https://doi.org/10.1111/j.1755-3768.1974.tb01755.x
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
More than 100 photopigment G protein-coupled receptors (opsins) have been sequenced and organized into six classes. Rod photoreceptors in various species have been found to express an opsin from one of the two rhodopsin classes, while cones express an opsin from one of the four remaining classes. It has now been discovered that salamander short-wavelength sensitive cones and green rods express the same opsin, while manifesting other features that classically distinguish rods from cones.
A great deal is known about the response properties of single neurons processing sensory information. In contrast, less is understood about the collective characteristics of networks of neurons that may underlie sensory capacities of animals. We used functional magnetic resonance imaging to study the emergent properties of populations of neurons processing motion across different brain areas. Using a visual adaptation paradigm, we localized a distributed network of visual areas that process information about the direction of motion as expected from single-cell recording studies. However, we found an apparent discrepancy between the directional signals in certain visual areas as measured with blood oxygenation level-dependent imaging compared with an estimate based on the spiking of single neurons. We propose a hypothesis that may account for this difference based on the postulate that neuronal selectivity is a function of the state of adaptation. Consequently, neurons classically thought to lack information about certain attributes of the visual scene may nevertheless receive and process this information. We further hypothesize that this adaptation-dependent selectivity may arise from intra- or inter-area cellular connections, such as feedback from higher areas. This network property may be a universal principle the computational goal of which is to enhance the ability of neurons in earlier visual areas to adapt to statistical regularities of the input and therefore increase their sensitivity to detect changes along these stimulus dimensions.
1. Whole-cell current responses to brief flashes were obtained from voltage-clamped 'on' bipolar cells in dark-adapted dogfish retinal slices. When internal Ca2+ was buffered to low levels, the current-voltage (I-V) relation of their flash responses was linear, with a reversal potential near 0 mV. 2. On elevating internal Ca2+ the light-dependent I-V relation showed outward rectification, such that the current response to a flash decreased e-fold for a hyperpolarization of 22 mV. 3. Inclusion of a CaMKII inhibitory peptide in the patch-pipette solution removed the rectification even in the presence of 50 microM Ca2+. 4. These results are consistent with CaMKII phosphorylation of cGMP-activated channels leading to a voltage-dependent reduction in conductance (outward rectification) and a reduced light response. The voltage-dependent property suggests that phosphorylation creates an energy barrier near the outer part of the channel, reducing the flow principally of monovalent cations. 5. This is the first reported instance of CaMKII phosphorylation acting to change the electrical characteristics of a membrane channel from linear to rectifying. 6. Ca2+-dependent desensitization by background light and channel rectification may underlie the change in centre-surround organization of the visual system with light adaptation.